Actuators of the pulling type, actuated by the explosion of a capsule, are disclosed in prior U.S. Pat. Nos. Patrichi 4,054,032; Leaman 3,024,592; Cordell 3,594,890; Williams 3,893,298. The Patrichi patent discloses an actuator wherein the explosive cartridge is mounted in one end of the cylinder in which the piston is slidable with its pull rod projecting from the other end of the cylinder, the pressurized gas being directed, through a transfer tube, into a chamber extending through the piston and into the piston shaft, from which it is directed outwardly through a lateral port in the shaft into a sealed space behind the piston, so as to move the piston in a direction to exert a pull upon the shaft and a pull-actuated device connected thereto. The Leaman patent discloses a cylinder in which a piston is slidable, the piston having a stem provided with an axial bore and radial ports for transferring the explosive gases to the back side of the piston for retracting the stem. The explosive capsule is mounted in the head of the piston. The reference does not disclose a transfer tube for directing the gas of explosion into the piston. In the present invention, the explosive charge is contained in a capsule mounted in the side of the cylinder, thus simplifying the construction.